High-alpha cellulose



United States Patent 2,805,169 Patented Sept. 3, 1957 Incorporated, Shelton, Wash., a corporation of Delaware No Drawing. Application July 18, 1955, Serial No. 522,855

12 Claims. (Cl. 106-463) This invention relates to high-alpha cellulose wood pulp and has for its object the provision of certain improvements in such pulp, and a process of producing viscose solution from the pulp. The invention is particularly concerned with high-alpha cellulose wood pulp primarily advantageous for use in the viscose and acetate processes, and provides improved pulp of this character comprising an added non-ionic water-soluble surfactant consisting of a hydrophobic organic nucleus having attached to it at least two polyethylene terminal units.

The non-ionic surfactants incorporated in the wood pulp are carried along through the various stages of the viscose process and produce important beneficial results in steeping by reducing foaming, in ease of shredding, better filtration, increased fatigue of tire cord made of the viscose, and are particularly effective in the dispersal of resins of the pulp, and as modifiers in the spinning of tire cord.

Refined dissolving pulps usually contain up to 0.15% (based on the bone dry weight of the pulp) of residual natural ether extractable resins. When such residual resins are present in pulp, even in smaller or larger amounts, they exercise a pronounced detrimental effect on the fatigue of filaments made from the pulp by the viscose process. This reduction in fatigue has especially pronounced adverse effects when the filaments are used in tire cord and the like which requires sustained high strength.

In the production of wood pulp, it is not commercially practical under prior practices to remove all of the resins from the refined pulp, thereby eliminating their detrimental effect on tire cord fatigue life.

While I do not wish to predicate this invention on any theory as to the unexpected results achieved, it appears that in the viscose process the non-ionic surfactants disperse the resins not only within the viscose but also keep them in dispersion after coagulation either remaining within the filaments in such dispersed state, or at least being partly washed out of the filaments in dispersed state. The filaments produced do not contain the usual beads or agglomerates (visible under magnification) of natural resins found scattered at random and forming sections of weakness in the filaments. In any event, the fatigue life of the filaments is very materially increased by the solubilizing or dispersion of these resins.

When the non-ionic surfactants are added to pulp of low ether extract used in the viscose process they improve the operation of shredding the alkali cellulose but without the detrimental effect on fatigue of the natural wood resins or without the detrimental effect on fatigue caused by surface active agents which have hitherto been used for replacing the natural wood resins to aid the shredding operation.

.The non-ionic surfactants introduced into the reacting constituents of the viscose process as aforementioned give the additional benefits of improving the brightness and color of the yarn or cord and suppressing spinneret crater 2 ing. The term cratering refers to the formation of incrustations inside and or around the outside of the holes of the spinnerets in spinning, ich have the effect of reducing the size of the filament causing broken or faulty filaments and other difficulties, In fact, the suppression of spinneret cratering is equal or superior to that achieved by materials used specifically forthat purpose.

In the preparation of sheets from refined Wood pulp, the purified fibers are first obtained in the form of a slurry in water. The non-ionic surfactants may be incorporated in the wood pulp at any stage in the production of the pulp sheet from the wet fiber slurry. For treating the pulp, the compounds may be incorporated either in the bulk before sheet formation or in the sheet at any stage prior to or after the completion of the drying as by spraying the pulp with an aqueous solution or dispersion. A most practical and convenient method of securing the incorporation of the non-ionic surfactants prior to completion of drying is to incorporate the compound in the refined wood pulp while it is on the sheet forming machine by means of sprays or a rotating roll. Such application may be made to the wet pulp web subsequent to the mechanical removal of water by pressing, or later at any stage while it is passing through thhe hot dryer rolls prior to completion of drying.

For improving mercerization in the viscose process, the surfaces of the sheets, and preferably each individual fiber, should be completely treated. Where, however, the main purpose of treating the pulp is either to conveniently and accurately add the non-ionic surfactants for purposes of minimizing the detrimental effect of pulp resins on filtration, resin dispersal, fatigue and for suppressing cratering, or to improve the shredding operation, then substantial improvements may also be obtained by treating only portions of the sheet and even by application after drying. For example, for such purposes, the surfactant addition may be applied in the form of a strip during the operation where the dried pulp in roll form is being cut into the form of sheets.

The non-ionic surfactants used in the product and of the invention are compounds having peculiar chemical structures and result in surprising improvements in various stages of the viscose process not achieved with the non-ionic surfactants heretofore incorporated in the viscose processing materials. Such compounds for use in my invention are water-soluble non-ionic compounds which consist of a hydrophobic compound of low water solubility containing at least 2 active hydrogens substituted by at least 2 terminal polyethylene oxide groups each containing from 1.6 to 700 ethylene oxide units.

The compounds used in the product and process of the invention may be represented by the formula:

wherein R is a polypropylene-containing nucleus of an organic hydrophobic compound of low water solubility in which at and y have average values for particular copolymers of 10 and 19;, 3.3 and 28; 6 and 28; 15.5 and 28; and 106 and 28, respectively. In one especially 3 effective block copolyrner, the average vaiues of x and y are 15.5 and 28 respectively, x varying from 11 to 17 depending upon the total iuolecular weight, and the \Zalue'oi y varying firom26 to 31, depending uphn the totalmolecular weight and the value of 3c. Block co- 9%??? p sl sqlr n. u a sh i. r pr sen amass. v lues ftrom. & to. 11.2. when. aid nucleus. s cemh ne with ion; Bflly fihylr tle x de radic ls he. c mpcundis. represented; by the.

formula:

in which x and y have average values of; from 2 .8 to 43 and 3 to 17.2 respeetive1 ,'the'compound is efiective for use'in the process of the invention. 'Such components are manufactured by the Wyanclotte Chemicals Corporation and sold under the trademarkTetronics. 'letronics 304, 504, 701, 702, 704, 707-; 904 and 908 having average values of x and y of 3.5 and.3 0, 8.1 and 713,118,

and 11.6, 5.2 and l1., 12.8 and 11.6, 47.0 andlll6,

18.3 and 172, and'43 7 and: 17.2 respectively; are especial ly' suitable for use in the invention.

The effective proportion of the non-ionic surfactants,

either as regards incorporation in the wood pulpjor for purposes of'impr'oving any stage in the viscose process is 0.02 to 0.20% based on the weight of bone dry pulp.

Ahove this'ra'nge in generahno additional" advantages are'ob'tai ried and particularly as 'regards 'to pulp a disadvantage may result in that the sheet will tend to become undesirably soft For treatment ofjpulp for use in acylation processes, a suitable propdrtion for adding the polymers is trorh 0.02 to 015% based: on the weight of bone'dry pulp, although larger proportions may be added if desired.

"The sheets of wood pulp treated prior to completion t drying with the non-ionic surfactants have markedly improved'prop'erties when used in aou'ebus reaction proc esses and particularly those involving a mercer iaing step as in the viscose process. Iii these adueous processes, the treated pulp sheets: are wetted an d penetratedmore, rapidly and uniformly by water orsodium hydroxide solution, the case of the latter giving more uniform mercerization. This may be demonstrated by the follownig rapid test for comparing the absorbency. of the sheets of dried pulp. in the following example.

Example I- Absorbency is determined by allowing a drop of NaOH solution to fall on the pulp sheet from a height of one,

to two centimeters and measuring the timejrequiredfor the disappearance of the, drop into the sheet.

A sample of pulp when treated with one of the afore mentioned surfactants in water solution and redriied.

ess by the non-ionic surfactaiits as herein incorpgrated it"; pnlp isl neat y 'diifiereiit'ifro'm eifect under s ilar circumstances of fnorrlrial surface iactive;agefits whiehi gehe'rally-do nbt aus'eiinprev'ed absorptivity or penetra tion' of the pulp by caustic soda solutions of mercerizing strength.

When alkali cellulose prepared by the improved mercerizing process or the improved mercerizing and shredding process of the invention is utilized in the viscose rayon process, certain further improvements are efiected in the subsequent steps of xanthating, dissolving, and filtering. In viscose solutions there is usually a certain amount of undissolved fibers and gel like material due to the incompleted reaction of the cellulose with carbon bisulfidc. during. xanthation. Prior to spinning, the viscose solutions are filtered several times to remove gels and undissolved fihers. In the event that the viscose solutions contain excessiye amounts of undissolved and partly dissolved fibers filtration is an expensive opera tion. In such cases, the filters become rapidly clogged and the filter media for example cloth, must be changed equsnflr ol er. mantis sw w P s r h in a reasonab letirne. Ereguent changing of the filter'meie. s. elipfnsi aeat l rd t su ntisa filter cloth butasso in; view of; the considerable-amountflab r; iWQl QQ-Ai t 8 oi s every ime the filter isop ed Eur em gre, when the viscose so l u.

so lar e htqt cr icus i e ike m terial;

processed into viscosecontai'ning 7 .5% cellulose and" sodium hydroxide with a filterability valueof 35.00:

This viscose was spun intohigh tenacity yarn of- 1 l00 denier extruding it at a salt index 7 of- 5 .5 into aspin bath-containing 9%-HsS04, 23% Na'2SO4, 3.5% ZnSOs,

with: no. trouble dueto cratering. When this yarn was washed in the usual manner,-color anddirt, possibly duectothe presence of sulfur compounds," were ade- (11131611.: reduced; v This.;.washedz yarn was twisted to produce tire cord of -'2450.-;denier.-ha-ving a fati-gue life of-285- minutes;

(Iza)i"lrhis same pulpbut; without the'added'Pluronic L+64t yielded: auviscose-sof: 3000 viscose filtration; but

gases severegcraterings during-i spinning, gave yarn still containing some; slight amounts of colored sulfur compounds, and gave. cord; havingla. fatigue life of only 25 3 minutes.

(gyl'l'hisisamexpulpnreatedlwith an added 0. 10%* of mixture ofacommonlyluused cratering agents yielded aviscose of 3000 viscose. filtration, gave satisfactory protection; agaiust.:crateriug,. but:- g'ave yarn: more diflicult to washttree'gfr omtsulfur compounds than the untreated pulp, and; gavescondehaving asfatiguelife ofonly 231;

(d): repcateof (a) bu'tewith 10% added Pluronic Lrfitsgavega .viscosecfilterabilityi of 3 /00, no: cratering; goodl=yarntcolor zand :cord with-a fatigue lifeot Z64:

( a):Asrepeats'offlclibuttwith .1.0 of the same anticratering agent gave a viscose filterability of only -340j (aft-A cellhlose pulp containing an excessively large &. g f l lll-y 1 lt9 9. .'Sa isf ry in, hat so a l s-Sm lls? ee ikes ti leste o passugh. h clam-w th ad er e ct nv e p n 6 amount (0.67%) of naturally occurring resin was'treat-- ed with 0.5% Pluronic L-64 and processed into viscose having a filterability of 1400. The viscose was spun with no spinning difliculties into 1100 denier tire cord yarn. The yarn was converted into 2450 denier tire cord which showed no broken filaments and had a fatigue life of 200. Cross-sections of the filaments of this, cord showed practically no agglomerated resin parbility having from 2 to 4 active hydrogens and in which ticles or filaments distorted from the resin agglomerates. x varies from 1.6 to 700 and n equals the number of (b) This same pulp without the added non-ionic poly- 10 active hydrogens. v mer gave a viscose filtration of only 230, gave 'much 2. An improved high-alpha cellulose dissolvingpulp spinning difiiculty as evidenced by worming and broken, as defined in claim 1 in which the non-ionic compound filaments, and yielded a cord having a fatigue life of is a block copolymer having the formula: only 4. Cross-sections of. filaments revealed ,(under' 7 magnification) many large resin agglomerates which led to brittleness. H!

soluble non-ionic compound represented-by the formula:

wherein R is a polypropylene oxide-containing nucleus of an organic hydrophobic compound of low water solu- Example 11 i (a) A tire cord grade cellulose pulp (96% alpha cellulose) containing 0.10% of natural ether extractable 2O resin was treated with 0.10% of Tetronic 704. and processed into viscose containing 7.5% cellulose and 6.5% sodium hydroxide with a filterability of 2640.

This viscose was spun into high tenacity yarn of 1650 denier by extruding it at a salt index of 5.5 into 2 a spin bath containing 9.4% H2SO4, 23.3% NazSO4, 3.5% ZnSO4, with no trouble due to cratering. When this yarn was washed in the usual manner, color and dirt, possibly due to the presence of sulfur compounds, were adequately reduced.

in which the average values of x and y vary from 3.3 to 106 and from 19 to 31 respectively.

3. An improved high-alpha cellulose dissolving pulp as defined in claim 1 in which the non-ionic compound is a block copolymer having the formula:

in which the average values for x and y are about 15.5 and 28.respectively.

t 4. An improved high-alpha cellulose dissolving pulp as defined in claim 1 in which the non-ionic compound '30 is represented by the formula:

H OCH2CH2 r OO3HB T (o3H0 ,,-(oH0H,0 ,H

'in which x represents average values of from 3.5 to V 437 and y represents average values of from 3 to 17.2.

(b) This same pulp, but without the added Tetronic A '5 An improved high-alpha cellulose dissolving pulp 704, yielded a viscose with a filterability of 2400. The asd'efined in'claim 1 in which the non-ionic compound yarn still contained some slight amounts of colored L0 is represented by the formula:

This washed yarn was twisted toproduce tire cord of 3700 denier having a fatigue life of 327 minutes.

sulfur compounds and gave a cord having a fatigue life of only 305 minutes.

Example V A premium grade tire cord pulp (96% alpha-celluin. which x and y have average values of about 3.5 and 3.0 respectively.

6. An improved high-alpha cellulose dissolving pulp as defined in claim 1 in which the non-ionic compound 1s represented by the formula:

lose) containing 0.06% of natural ether extractable resin was treated with an added 0.10% of a non-ionic sur- 11,6 respectively.

factmt Tetl'ODlC and converted lIltO VISCOSE and tll'e h7 The improvement in the production of filaments by cor t e viscose process which comprises forming a viscose Th1s tire 60 had a fatlgue llfe P 305 compared solution from wood pulp containing not more than with 60 from untreated P p havlng fatlgue llfe of 0.5 based on the bone dry weight of the pulp of ether 291. extractable resins of the wood and from 0.02% to In the foregoing examlfles the vahles for filtration p- 0.5 of a water-soluble non-ionic compound which conresent the amounts of viscose solution passing through the filter before it becomes plugged and inefiective.

This application is a continuation-in-part of the application of Paul Henry Schlosser, Kenneth Russell Gray and Reid Logan Mitchell Serial No. 289,883, filed May 24, 1952.

I claim:

in which x and y have average values of about 12.8 and solubility containing from 2 to 4 active hydrogens substituted by from 2 to 4 terminal polyethylene oxide groups each containing from 1.6 to 700 ethylene oxide units.

8. The process according to claim 7 in which the 1. An improved high alpha cellulose dissolving Wood non-ionic compound is a block copolymer having the pulp suitable for conversion into cellulosic solutions formula: which pulp contains residual ether extractable resins. of 2 )Z( 2 )y( I HB )zH the wood, and from about 0.02% to about 0.5% based on the bone dry weight of the pulp of an-added watersists of an organic hydrophobic compound of low water 

1. AN IMPROVED HIGH-ALPHA CELLULOSE DISSOLVING WOOD PULP SUITABLE FOR CONVERSION INTO CELLULOSIC SOLUTIONS WHICH PULP CONTAINS RESIDUAL ETHER EXTRACTABLE RESINS OF THE WOOD, AND FROM ABOUT 0.02% TO ABOUT 0.5% BASED ON THE BONE DRY WEIGHT OF THE PULP OF AN ADDED WATERSOLUBLE NON-IONIC COMPOUND REPRESENTED BY THE FORMULA: 